The present invention relates to roofing piles for use in constructing built up roofing systems and particularly, to a method for making improved roofing plies and the application of the same to a roof.
U.S. Pat. No. 4,567,079 discloses a lightweight roofing ply, sheet or membrane intended to provide improved ventability and attachment in a built up roofing system (BUR) comprising successively stacked sheets. To effect this, the patent provides a tar saturated mat having a plurality of holes along its longitudinal margin to facilitate flow of the tar bonding agent between the sheets. While the holes do in fact, make the flow of the bonding agent easier, it has been found that the sheet or ply made in accordance with the aforementioned patent, has severe drawbacks mitigating against its wide acceptance rise giving use to great difficulty in applying the sheet and in providing a firm and secure attachment in the BUR system.
In particular, it has been found that when a hot tar bonding agent is applied to the sheet during the build-up of the roof, the sheet has uneven and unpredicable stretch and cooling characteristics so that the ultimate roofing is neither uniform nor smooth. Air bubbles tend to occur between sheets and the bonding agent does not adhere securely. Further, upon laying lengths of sheet ply along the roof, it has been found that the sheets tend to warp and curve along their length so that sheet linearity and alignment of successive sheets does not occur.
Accordingly, it is an object of the present invention to provide a lightweight roofing ply for use in built up roofing systems (BUR) which avoid the disadvantages and difficulties found in the prior art.
It is a specific object of the present invention to provide a roofing ply (i.e., sheet) for BUR systems which has uniform expansion and contraction characteristic under successive heating and cooling during application to the roof and which maintains a constant linearity, upon application.
In general, it is the object of the present invention to provide a roofing sheet for BUR systems which is easy to manufacture and easy to employ and which, at the same time, results in providing roofing which also has the ability of not only providing good protection, but is easy to apply and use to cover a roof.
The foregoing objects and advantages, together with numerous others are set forth in the following disclosure.